What does a widened QRS complex indicate?

Extremely wide QRS which is difficult to delineate from the ST segment and T wave. This is approaching a sine-wave pattern, and indicates end-stage hyperkalemia which usually precedes an unstable tachy- or bradyarrhythmic cardiac arrest. Even in the absence of electromechanical dissociation which is present in severe hyperkalemia, this disorganized and morbidly wide QRS complex is likely not providing a reasonable cardiac output. 

Hyperkalemia was not suspected immediately after this ECG. Given that the patient had chest pain on arrival, and hyperkalemia had not been suspected on the initial ECG, in a patient with acute worsening, one can understand why acute STEMI +/- intermittent VT/VF may have seemed more likely to explain her acute change. A STEMI alert was called based on perceived ST elevations in the anterior leads V2-V4.

On the way to the resuscitation bay, the patient became unconscious and lost pulses. CPR was initiated. The monitor showed VFib, and she was shocked twice without conversion. On review of the initial ECGs, hyperkalemia was suspected at this point, and the patient received IV calcium and bicarb with ROSC achieved 1-2 minutes later.


Initial labs (~1hour prior to arrest) finally returned showing:
K = 8.1
BUN = 99
Cr = 6.84
Troponin = undetectable


A post-ROSC ECG was obtained just as a change in rhythm occurred:

The first 3-4 QRS complexes are very wide with bizarre morphology of QRS and ST-T-wave. The rhythm then changes to regular and tachycardic, with probable P-waves, (~120 bpm) for the remainder of the ECG.   
The patient's blood pressure on the arterial line dropped acutely:
This shows sustained polymorphic wide complex tachycardia. It is somewhere on the spectrum between polymorphic VT (PMVT) and VFib. The exact point on that spectrum is irrelevant, as the spectrum is more of a vortex ending in VFib arrest. The treatment for either is immediate, unsynchronized defibrillation.
Defibrillation was attempted several times, each with temporary improvement to a more organized wide complex tachycardia, then returning to PMVT/VFib:
Similar to prior
More calcium chloride and bicarb were administered. The exact amount is not available. Within minutes the patient achieved ROSC:
Sinus rhythm with much narrower (but still wide) QRS complex. There is perhaps a short QT and QTc interval here which may be caused by the calcium (a well described finding in hypercalcemia) which appears to have saved this patient's life. 

A combination of the Q wave, R wave and S wave, the “QRS complex” represents ventricular depolarization.

This term can be confusing, as not all ECG leads contain all three of these waves; yet a “QRS complex” is said to be present regardless.

For example, the normal QRS complex in lead V1 does not contain a Q wave — only a R wave and S wave — but the combination of the R wave and S wave is still referred to as the QRS complex for this lead.

The normal duration (interval) of the QRS complex is between 0.08 and 0.10 seconds — that is, 80 and 100 milliseconds. When the duration is between 0.10 and 0.12 seconds, it is intermediate or slightly prolonged. A QRS duration of greater than 0.12 seconds is considered abnormal.

The QRS duration will lengthen when electrical activity takes a long time to travel throughout the ventricular myocardium. The normal conduction system in the ventricles is called the His-Purkinje system and consists of cells that can conduct electricity quite rapidly. Thus, normal conduction of an electrical impulse through the atrioventricular, or AV, node, then to the ventricles via the His-Purkinje system, is fast and results in a normal QRS duration. When electrical activity does not conduct through the His-Purkinje system, but instead travels from myocyte to myocyte, a longer time is necessary, and the QRS duration is widened.

A widened QRS duration occurs in the setting of a right bundle branch block, left bundle branch block, non-specific intraventricular conduction delay and during ventricular arrhythmias such as ventricular tachycardia — all of which are discussed in detail inside their respective sections in ECG Reviews and Criteria.

What type of arrhythmia has a widened QRS complex?

How serious is a wide QRS?

Is wide QRS an emergency?

What might an overly large QRS wave indicate?